1. Field of the Invention
The invention relates to laminating a functional film onto an injection molded ophthalmic lens using the clamp pressure, mold temperature, and residual resin heat to cure a thermally curable glue, preferably an acrylate based glue, to facilitate the bonding between the film and the lens.
2. The Prior Art
In the manufacture of plastic lenses, the injection molded lens is removed from the mold for further processing to integrate specific functions such as anti-reflective, photochromic, or anti-scratch to the lens. Typically the lenses are cleaned and dip-coated with a tint coating, photochromic coating, anti-reflective coating, hard coating or other protective coating layers. The cleaning and dip-coating process requires a large investment of space, resources and energy.
Other approaches involve laminating a single or multi-layer functional film onto the lens. One technique known as film insert molding (FIM) places the film into the empty cavity of the injection molding machine. The molten resin is then injection molded into the cavity so that the high temperature melts the facing layer of the film, causing it to fuse to the subsequently solidified lens. By way of example, this technique is described in U.S. Pat. No. 5,827,614, U.S. Pat. No. 6,328,446, U.S. Pat. No. 6,814,896 and U.S. Pat. No. 6,659,608. A serious drawback of FIM, is the requirement that the facing layer of the film be the same or compatible with the lens resin, to obtain a fusion between the material of the facing layer of the film and the injected resin.
Another drawback of FIM, is related to the high temperature required to obtain melted resin which could degrade or partially destroy the functionality built into the film.
Accordingly, it would be desirable to provide a process for adding functional layers to a lens which has a greater degree of flexibility, and which maintains at a high level of quality the integrity of the film's functionality.